Dr. Ryan Stone (Bullock), a biomedical engineer from Lake Zurich, Illinois, is aboard the NASA Space Shuttle Explorer for her first space mission, STS-157. Veteran astronaut Matt Kowalski (Clooney) is commanding his final mission. During a spacewalk to service the Hubble Space Telescope, Mission Control in Houston warns the team about a Russian missile strike on a defunct satellite, which has inadvertently caused a chain reaction forming a cloud of debris in space. Mission Control orders that the mission be aborted and the crew begin re-entry immediately because the debris is speeding towards the Shuttle. Communication with Mission Control is lost shortly thereafter.